The present invention relates to a scanning optical system including a reading optical system for reading information on an object surface and an image forming optical system for forming an image on a destination surface such as a photoconductive surface.
Conventionally, a reading optical system as described below has been known. In the reading optical system, an object surface to be read, or scanned is illuminated by a lamp such as a fluorescent lamp. The light reflected on the object surface is directed to a sensor such as a CCD (Charge Coupled Device) line sensor through a converging lens, projection lens and the like. The line sensor thus outputs an image information corresponding to one scanning line of the image on the object surface. At the same time, the surface is relatively moved in the direction perpendicular to the direction of the line sensor. Thus, the reading optical system obtains a two-dimensional image information of the object surface.
With respect to an image forming optical system, an electrophotographic imaging method as described below is well known. In the image forming optical system, a laser beam carrying an image information is deflected by a polygonal mirror in order to scan a charged photoconductive surface of a photoconductive drum in a direction of the rotational axis of the photoconductive drum (main scanning). As the main scanning is being performed, the photoconductive drum is rotated (auxiliary scanning) so that the circumferential surface of the photoconductive drum is scanned by the deflected laser beam. Thus, the image forming optical system forms a latent image on the photoconductive surface of the photoconductive drum.
The latent image formed on the circumferential surface of the photoconductive drum is developed, i.e., a toner is applied to the latent image to form a toner image. The toner image is transferred onto a recording sheet, and fixed thereonto.
In an apparatus which is required to have an image reading function and an image forming function, e.g., a facsimile machine or a digital copy machine, two different optical systems: the reading optical system; and the image forming optical system should be provided. In such an apparatus, improvement has been desired to reduce the entire size of the apparatus, and to decrease the manufacturing cost thereof.